1. Field of the Invention
The present invention relates generally to molecular oncology. More specifically, the present invention relates to oncogene identification by transformation of RK3E cells and uses thereof. Even more specifically, the present invention relates to the newly identified oncogene Gut-Enriched Krüppel-Like Factor/Epithelial Zinc Finger (GKLF, or termed KLF4, Krüppel-like factor 4) and applications of such gene in medical diagnosis and treatment.
2. Description of the Related Art
Cellular oncogenes have been isolated by characterization of transforming retroviruses from animal tumors, by examination of the breakpoints resulting from chromosomal translocation, and by expression cloning of tumor DNA molecules using mesenchymal cells such as NIH3T3. Several human tumor types exhibit loss-of-function mutations in a tumor suppressor gene that lead to activation of a specific oncogene in a large proportion of tumors. For example, c-MYC expression is regulated by the APC colorectal tumor suppressor; expression of GLI is activated by loss-of-function of PTC in human basal cell carcinoma and in animal models; E2F is activated by loss-of-function of the retinoblastoma susceptibility protein p105Rb; and RAS GTPase activity is regulated by the familial neurofibromatosis gene NF1. The comparative genomic hybridization assay and related methods have shown that numerous uncharacterized loci in tumors undergo gene amplification. These observations, and the infrequent genetic alteration of known oncogenes in certain tumor types, suggest that novel transforming oncogenes remain to be identified.
One limitation to the isolation of oncogenes has been the paucity of in vitro assays for functional expression cloning, as several oncogenes are known to exhibit cell-type specificity. For example, GLI, BCR-ABL, NOTCH1/TAN1, and the G protein GIP2 have been found to transform immortalized rat cells, but not NIH3T3 or other cells, demonstrating the potential utility of alternate assays for oncogene expression cloning. While most studies have used NIH3T3 or other mesenchymal cells as host for analysis of oncogenes relevant to carcinoma, the potential utility of a host cell with epithelial characteristics has been discussed.
The prior art is deficient in methods of identifying carcinoma oncogenes by utilizing a host cell with epithelial characteristics. The present invention fulfills this long-standing need and desire in the art by disclosing methods of oncogene identification that involves transformation of RK3E cells.